U.S. attack helicopters have killed 17 armed al-Qaida militants in clashes near Baquba in Diyala Province north of Baghdad. The clashes occurred as part of a house-to-house U.S. military offensive designed to root out insurgents in strongholds around the Iraqi capital.

Also Friday, the U.S. military announced that a U.S. soldier has been killed during fighting in Baghdad, raising the American death toll to at least 15 since Tuesday. The military said the soldier was killed Thursday during combat operations in the southwestern section of the capital.

U.S. Defense Secretary Robert Gates says American forces face more tough fighting in Iraq as they go into areas they have not been in for some time.

In the deadliest attack against U.S. forces Thursday, a roadside bomb blast in Baghdad killed five U.S. soldiers, three Iraqi civilians, and one Iraqi interpreter.

Also on Thursday, U.S. and Iraqi forces launched three raids in Baghdad against networks behind roadside bomb attacks. A military statement says 18 suspected militants were detained and weapons were confiscated.

Thousands of U.S. troops are combing areas north and south of Baghdad in stepped-up operations against al-Qaida and allied insurgents.

In other violence Thursday, a suicide truck bomber killed at least 16 people and wounded about 70 others in the northern Iraqi town of Sulaiman Beck, south of Kirkuk.

Some information for this report was provided by AFP and AP.